Methods of storing natural gas which includes methane as a main component have been known for many years; for example see U.S. Pat. No. 2,535,148 and U.S. Pat. No. 3,232,725. More recently, the use of metal organic frameworks (MOFs) for storing gas including methane as a main component has been proposed in for example U.S. Pat. No. 5,862,796 & EP 0 727 608 A2. For example, U.S. Pat. No. 5,862,796 describes a gas storage apparatus for use in storing a gas containing methane as its main component which is hereby incorporated by reference in its entirety. The apparatus includes a pressure vessel accommodating therein an organometallic complex (a MOF). Storage of the gas takes place by adsorption and retention of the gas inside the MOF at increased pressure and normal/ambient temperature. Further, for releasing the gas from the apparatus (i.e. desorption of the gas from the MOF), the inside pressure of the vessel is reduced, whereby the gas is desorbed from the MOF to be discharged out of the apparatus for use in a certain application. In general MOFs are able to store methane efficiently at elevated pressure and normal temperature conditions within a relatively limited volume.
There is however a need to increase further the storage capacity of porous adsorbent frameworks such as metal organic frameworks and increase the deliverable capacity of such porous adsorbent frameworks.